1. Field of the Invention
The present invention relates to an optical fiber fusion splicer, and particularly, to an optical fiber fusion splicer that has coating clamp installation bases, which advance and retract with respect to a heating and fusing portion that heats and fusion-splices optical fibers to each other, on both sides of the heating and fusing portion and that is provided with coating clamps for gripping and fixing the optical fibers on the coating clamp installation bases.
2. Description of the Related Art
As optical fiber fusion splicers, there are provided an apparatus (single-core machine) that performs discharging and heating on a pair of single-core optical fibers, which face each other in the longitudinal direction, between a pair of electrode rods to fusion-splice the single-core optical fibers, and an apparatus (multi-core machine) that performs discharging and heating on multi-core optical fibers (tape fibers) between a pair of electrode rods to collectively fusion-splice the multi-core optical fibers.
Additionally, as an optical fiber fusion splicer in the conventional art (hereinafter, also simply referred to as a fusion splicer), an apparatus having the following functions and configurations is widely provided (Japanese Unexamined Patent Application, First Publication No. H6-160662).
(1) Optical fibers are irradiated with light from two directions using two illumination light sources, and the optical fibers are biaxially imaged (biaxial observation) from two directions using two lenses and two cameras.
(2) A pair of V-grooves are provided on both sides of a heating and fusing portion that is a space between a pair of electrode rods.
The pair of V-grooves are configured so that the tips of the optical fibers to be fusion-spliced can be positioned between the pair of electrode rods.
Additionally, the pair of V-grooves are provided via the heating and fusing portion so as to run along the upper surface of an apparatus body where the pair of electrode rods are arranged, and are provided via the heating and fusing portion so as to be arranged on both sides in a direction (left-and-right direction) perpendicular to a direction (front-and-rear direction) in which the pair of electrode rods face each other.
As the optical fiber, a coated optical fiber, such as an optical fiber core or an optical fiber stand, is used in many cases.
An optical fiber glass portion obtained by removing the covering from the tip of an optical fiber (covered optical fiber) is arranged on a V-groove, and is gripped between a fiber clamp member that presses the optical fiber glass portion against the V-groove from above, and the V-groove.
Two sets of the V-grooves and the fiber clamp members are provided in correspondence with the two optical fibers arranged in the left-and-right direction.
(3) In order to grip covered portions of the left and right optical fibers, movable coating clamps are provided to move in the left-and-right directions of the apparatus body, or fiber holders are respectively arranged on both sides in the left-and-right direction so as to move in the left-and-right direction of the apparatus body.
(4) The discharge generated between the electrode rods is sensitive to air currents, and fluctuation of the discharge also occurs by receiving a slight air current.
Thus, a configuration provided with an openable and closable windshield cover that covers the electrode rods, the V-grooves, the fiber clamp members, and the coating clamps or the fiber holders is adopted as the fusion splicer.
The windshield cover is configured so as to provide a sealing structure in which the electrode rods or the like are covered to prevent air currents from reaching the discharge portion between the pair of electrode rods.
The windshield cover can be openable and closable by a manual operation.
As for the general fusion splicers in the conventional art, the operation of mounting the optical fibers is as follows.
(a) Coating clamp system: openable and closable lid portions of coating clamps attached to the apparatus (fusion splicer) are closed to pinch and grip single-core optical fibers with the coating clamps.
The coating clamp has the lid portion pivotally attached to the base plate fixed onto the coating clamp installation base of the apparatus (fusion splicer).
Large-sized coating clamps are able to grip single-core optical fibers with various diameters of covering.
Additionally, since the coating clamps are attached to the apparatus (fusion splicer), there is no possibility that the coating clamps will be lost.
(b) Fiber holder system: coating clamps (hereinafter also referred to as fiber holders) detachably placed on the coating clamp installation bases of the fusion splicer are used.
After optical fibers are gripped and fixed by the fiber holders detached from the coating clamp installation bases of the fusion splicer, the fiber holders are placed on the coating clamp installation bases of the fusion splicer.
The fiber holder has a base plate, and an openable and closable lid portion that is pivotally attached to the base plate.
The fiber holder grips an optical fiber between the base plate and the lid portion closed with respect to the base plate.
The optical fiber can be easily mounted on the fiber holder by respective processes of covering removal, cutting, and fusing.
However, in the Fiber holder system, it is necessary to prepare various kinds of fiber holders according to the diameter of covering or the number of core wires.
In the fusion splicing operation of optical fibers using the fusion splicer in the conventional art, first, the fiber set operation of mounting the optical fibers, the tips of which are subjected to covering removal (exposure of optical fiber glass portions), cleaning, and regular size cutting, on the fusion splicer is performed in a state where the windshield cover is opened.
The fiber set operation of the coating clamp system fusion splicer means the operation of pinching the covered portion of the optical fiber with the coating clamp.
The fiber set operation of the Fiber holder system fusion splicer means the operation of placing the fiber holder pinching the covered portion of the optical fiber on the coating clamp installation base of the fusion splicer.
If the mounting of the optical fibers to the fusion splicer is completed, the windshield cover is closed, and subsequently, a splicing start switch of the fusion splicer is turned on.
As a result, the fusion splicer advances the coating clamp installation bases toward the heating and fusing portion between the electrode rods.
In the structure in which the coating clamp installation base is advanced, a motor (installation base advancing motor) is driven to drive to move (advance) a moving and driving shaft of a drive mechanism via a motor gear and a drive mechanism gear, and the coating clamp installation base is pushed and advanced toward the heating and fusing portion by the moving and driving shaft.
This causes an optical fiber to advance to a predetermined position.
Next, the tips of the left and right optical fibers (optical fiber glass portions) are melted by the discharge between the electrode rods.
Then, the melted optical fibers are fusion-spliced by being further pushed in the axial direction while continuing to be heated by the discharge.
The discharge between the electrode rods stops automatically after being performed for a predetermined period of time.
The fusion splicer automatically performs a tension test for inspection of a spliced portion after the discharge stops.
Hereinafter, this tension test is also referred to as a proof test.
After the completion of the fusion splicing, the windshield cover is manually opened and the optical fibers are taken out.
In the proof test, the installation base advancing motor is rotationally driven in a direction opposite to the rotational direction thereof at the time of the advancement of the coating clamp installation base to retreat the moving and driving shaft of the drive mechanism.
As a result, a spring for a proof test installed between the base member and the coating clamp installation base of the fusion splicer elastically biases and retreats the coating clamp installation base in a direction away from the heating and fusing portion.
The retreat of the coating clamp installation base stops as a constant tension acts on the optical fibers that are spliced to each other and joined integrally, by the elastic biasing force of the spring for a proof test.
The moving and driving shaft of the drive mechanism retreats to a position where the moving and driving shaft does not come into contact with the coating clamp installation base the retreat of which has stopped as the tension acts on the mutually spliced optical fibers.
A gap is secured between the moving and driving shaft and the coating clamp installation base of the drive mechanism.
As a result, the tension test of the spliced portion between the optical fibers is performed by the elastic biasing force of the spring for a proof test.
For the lid portion of the coating clamp of the Coating clamp system fusion splicer, there is widely adopted a configuration having a lid plate that is pivotally attached to the base plate, a gripping rubber member that is provided at the lid plate to grip and fix the optical fiber together with the base plate when the lid plate is closed with respect to the base plate, and a clamp spring that is provided at the lid plate to elastically bias the gripping rubber member toward the base plate.
This coating clamp can maintain a state where the lid plate is closed with respect to the base plate, with an attractive force generated when a magnet assembled into the base plate magnetically attracts a ferromagnetic body, such as iron or the like, which is provided at the lid plate.
The attractive force of the magnet is adjusted to a degree such that an operator can open the lid plate closed with respect to the base plate with an operator's fingers.
The present inventor has verified the relationship between a force (hereinafter also referred to as a clamp load) that grips an optical fiber between the gripping rubber member, and the base plate with a magnetic attractive force, and a regulating force (hereinafter also referred to as a fiber grip force) that regulates slipping of an optical fiber with respect to the gripping rubber member and the base plate, regarding a general coating clamp used for the Coating clamp system fusion splicer.
The results are shown in FIG. 30.
FIG. 30 shows the results when the relationship between the clamp load and the fiber grip force when the clamp load is made to act is investigated, using various optical fibers, regarding the general coating clamp.
Proof tests are carried out by making a tensile load of 1.96 N to 2.26 N act on the optical fibers.
From FIG. 30, in order to stably maintain a gripped and fixed state without causing slip of the optical fibers even if the coating clamp makes a tensile load of 1.96 N to 2.26 N act on the optical fibers, it is necessary to set the clamp load to 2.94 N or more.
As the clamp spring of the coating clamp, a clamp spring that generates a pressing force of about 3.43 N is adopted in order to obtain a clamp load of 2.94 N or more.
Additionally, as the coating clamp, a coating clamp with grip force (hereinafter also referred to as a lid closing force) that acts between the base plate and the lid plate with the attractive force of the magnet of 3.43 N or more is adopted in order to realize stable maintenance in a state where the lid plate is closed with respect to the base plate.
However, in the coating clamp, with a lid gripping force of 3.43 N or more, it is necessary to strongly pull up and open the lid plate with respect to the base plate against the attractive force of the magnet with an operator's fingers when the lid portion closed with respect to the base plate is manually opened.
For this reason, there is a case where the operation of opening the coating clamp and taking out an optical fiber after the completion of a proof test takes substantial time and effort.
Additionally, the fusion splicing operations of hundreds of optical fibers may be performed per day.
For this reason, in the fusion splicers, shortening of the operation time of the fusion splicing of the optical fibers and improvement of operability are required.
In addition, the fiber holder generally has a configuration in which the lid plate itself capable of being magnetically attracted by the magnet assembled into the base plate functions as a hold-down member that holds down an optical fiber toward the base plate.
In the fiber holder, the whole lid portion is constituted by the lid plate.
Similar to the coating clamp used for the Coating clamp system fusion splicer, even regarding the fiber holder, it is necessary to strongly pull up and open the lid plate with respect to the base plate against the attractive force of the magnet with an operator's fingers when the lid portion closed with respect to the base plate is manually opened.
Accordingly, similar to the Coating clamp system fusion splicer, even regarding the Fiber holder system fusion splicer, there is a case where the operation of opening the coating clamp and taking out an optical fiber after the completion of a proof test takes substantial time and effort.
In view of this, as the coating clamp, for example as disclosed in Paragraphs (0013) to (0018) and FIG. 1 of Japanese Unexamined Patent Application, First Publication No. H6-160662, there is suggested a configuration in which a lid plate (movable-side clamp 22) is openable and closable by normal and reverse rotational driving of a motor 25 provided at a coating clamp installation base (base 17 of the fusion splicer) with respect to a base plate (fixed-side clamp 18).
Moreover, in the coating clamp (gripping device) disclosed in Japanese Unexamined Patent Application, First Publication No. H6-160662, the movable-side clamp 22 (lid plate) functions as a whole lid portion.
In this coating clamp, a rack 21 coupled and fixed to the movable-side clamp 22 via a locking pin 22 is engaged with a pinion gear 24 coupled to an output shaft of the motor 25 at a base 17 of the fusion splicer.
Then, in this coating clamp, the rack 21 is lifted and lowered by the normal and reverse rotational driving of the motor 25 to open and close the lid plate with respect to the base plate.
Hereinafter, this coating clamp is also referred to as a motor driven coating clamp.
However, in the above-described motor driven coating clamp, it is necessary to arrange an opening and closing driving motor (hereinafter also referred to as a lid plate opening and closing motor) of the lid plate inside the fusion splicer.
Additionally, in that case, devices, such as a motor for the advance and retract operation of the coating clamp installation base, a motor for the focalization operation of a camera for imaging an optical fiber, and driving force transmitting parts transmitting the driving forces from these motors, are highly densely provided inside the fusion splicer.
Additionally, in the case of the fusion splicer that has a self-core-alignment function, motors for alignment of the optical fibers set in the V-grooves on both left and right sides are also provided inside the fusion splicer.
In this way, devices, such as a motor, are densely arranged inside the fusion splicer.
For this reason, when the lid plate opening and closing motor is assembled into the fusion splicer, apparatus designs are greatly influenced, and an increase in size and cost of the fusion splicer is unavoidable.
Additionally, since the motor driven coating clamp grips an optical fiber between the base plate and the lid plate with the driving force of the motor, it is necessary to continue supplying electric power to the motor in order to maintain gripping and fixing of a covered portion of the optical fiber, and the amount of power consumed is large.
For this reason, when the fusion splicer provided with the motor driven coating clamp is driven with batteries outdoors, the number of operations of fusion splicing up to battery exchange is small.
An object of the invention is to provide a fusion splicer that can realize shortening of the operation time of fusion splicing of optical fibers and improvement in operability at low cost, without nearly (or completely) affecting apparatus size, and that can avoid an increase in power consumption.